This invention relates generally to cooling passages in a wall, and, more specifically, to cooling passages in gas turbine engines such as, for example, in combustor liners and turbine blades and vanes thereof.
Gas turbine engines typically include structures such as combustor liners and stationary and rotating turbine blades and vanes which are subject to relatively hot combustion gases. The structures are typically provided with cooling passages for protection from the hot combustion gases. It is conventionally known that any passage or hole contained in a wall structure subject to stress results in a stress concentration about such hole which must be considered in determining the useful life of that structure.
Cooling passages typically utilized in gas turbine engines are generally circular in section. However, when a passage having a circular section is disposed at an angle in a wall, the section of that passage in a plane parallel to the plane of the wall is elliptical. Elliptical holes have major and minor axes, and, depending upon the orientation of principal stress with respect to the major and minor axes, stress concentrations about the hole may be generated which are either less than or greater than those associated with a circular hole. For example, in a wall subject to a principal, tensile stress in a single axis, the conventional stress concentration about a circular hole is equal to 3 and the conventional stress concentration about an elliptical hole is equal to 1+2a/b or 1+2b/a, where a and b represent the major and minor semi-axes, and are oriented either perpendicular or parallel to the principal stress, respectively.
Accordingly, the use in a wall of an inclined cooling passage having a circular section will generate an elliptical section, which, depending on its orientation with respect to the principal stress in the wall, can result in a stress concentration either less than or greater than that of a circular hole. A stress concentration greater than that of a circular hole will lead to an undesirable shortening of the life of the wall.
Accordingly, it is an object of the present invention to provide a new and improved wall having an inclined cooling passage therein.
Another object of the present invention is to provide a new and improved wall having a cooling passage of a predetermined section predeterminedly oriented with respect to principal stress in the wall for obtaining a reduced stress concentration.
Another object of the present invention is to provide a new and improved wall having an inclined cooling passage for improving useful life of the wall.